Highly selective and stable ZnO-supported bimetallic RuSn catalyst for the hydrogenation of octanoic acid to octanol

Abstract

• Octanoic acid was converted over RuSn supported on ZnO. • High conversion (99.4 %) and selectivity to octanol (93.0 %) were achieved. • Ru 3 Sn 7 alloy phase was responsible for the high hydrogenation activity. • Esterification was suppressed by optimizing the reaction condition. • RuSn/ZnO was exceptionally robust over 1000 h. The chemoselective hydrogenation of biomass-derived carboxylic acids is promising for the development of biorefineries. Herein, the selective conversion of octanoic acid to octanol over bimetallic RuSn/ZnO in a fixed-bed continuous reactor system, is reported. Almost complete conversion (99.4 %) of octanoic acid was achieved, with a remarkably high selectivity to octanol (93.0 %), when using specific reaction conditions (300°C, a weight hourly space velocity (WHSV) of 2 h −1 , and 30 atm H 2 ). Characterizations of the catalysts by BET, CO pulse chemisorption, ICP-AES, XRD, XPS and STEM-EDS revealed that the addition of Sn to Ru/ZnO resulted in the formation of a Ru 3 Sn 7 alloy phase as well as SnO x . Comparison with Ru/ZnO catalyst gives an insight that the presence of Ru 3 Sn 7 alloy was most likely the active site and it significantly improved the hydrogenation activity and selectivity to octanol. The SnO x and ZnO favored the formation of octyl octanoate by esterification of the formed octanol and octanoic acid, although it was successfully suppressed by optimizing the reaction conditions. Long-term stability tests revealed that RuSn/ZnO retained its activity for 1000 h with no coke formation. This study reveals the potential of RuSn/ZnO for the valorization of medium-chain fatty acids into value-added chemicals.